I noticed that one of my biggest weaknesses is getting my legs up onto footholds above my knee (something like this http://static.flickr.com/...44757_9ad842ff7e.jpg or this http://www.flickr.com/...6801@N05/3985575321/; especially when it is closer to being in line with the center of my body. I feel tightness in my glutes and my groin when I do this and often get really bad ass cramps if I push it too far. What kind of stretches/progression of stretches should I do to increase my flexibility to get my legs up higher? Thanks.

This might seem a little left field, but try very hard massage of your lower back, near the spine. To cut a long story short, 6 years ago I was diagnosed with osteoarthritis of the hips and told I'd need an immediate hip replacement. I was told there was no cure and it would only get worse. My wife and I developed a treatment based on intense massage of the lower back. Now I'm pain free, without drugs. As a side benefit, I've found I can now lift my feet enormously higher than I could previously. I've always done a lot of daily exercise, including pilates and yoga but these had little effect.

Best 'stretch' i found for this is to cross leg one over leg 2, with your ankle just above your knee. Then lay on your back and pull leg 2 underneath your hamstring. Carefull this puts a lot of pressure on your knee of leg one. Make sure to keep leg 1's toes pointed up (to your shin) to lower the pressure on your knee. Maybe i should find a pic for you if you need it. I would after that horrible explanition.

This problem seems to be amplified in the gym, I rarely experience it outdoors for some reason.

I generally start each gym sesh with gentle stretching, one of which involves finding a foot hold about 6" higher than I can statically reach with a foot. Now find two hand holds and place one foot on the foot hold and keep it there as you relax your weight, trying to touch the floor with the other foot. Switch feet and repeat.